Polyamides containing butyrolactone



June 27, 1967 T. F. CORBIN, JR. ETAL 3,328,341

POLYAMIDES CONTAINING BUTYROLACTONE Filed Sept. 9, 1963 P P w w m R G D D U W W O O E E u L m o m m n m o R A n C o D m 0 n o o E o o 7 6 5 4 3 2 I. Amm 5m m0 w2 mo m: mmm whzmj 5omfl$v wmnomo 02m PERCENT BUTYROLACTONE ADDED TO POLY (EPSILON CAPROLACTAM) CHIPS INVENTORS THOMAS F. CORBIN JR. KEITH D. DODSON United States Patent 3,328,341 POLYAMIDES CONTAINING BUTYROLACTONE Thomas F. Corbin, .l'r., and Keith D. Dodson, Asheville, N. C., assignors to American Enira Corporation, Enka, N.C., a corporation of Delaware Filed Sept. 9, 1963, Ser. No. 307,428 7 Claims. (Cl. 26045.8)

This invention relates generally to modified synthetic linear polyamides and more particularly to the production of poly(epsilon-caprolactam) which has been modified to decrease its dyeability and improve the light stability.

It is well known to treat polyamides with various agents in order to increase their afiinity for certain dyes. This is a relatively common practice with such polyamides as polyhexamethyleneadipamide (nylon 66) because of its inherent low order of dyeability. The reaction is usually one in which the polymer chain is substituted with additional reactive groups or shortened to give more end groups, thereby providing an increased number of dye sites and resultant increase in dyeability with respect to various acid dyes. However, in the case of polyamides such as poly(epsilon-caprolactam) (nylon 6), which possesses a larger number of available dye sites in relation to polyhexamethyleneadipamide and thus is easier to dye, it is sometimes desirable to decrease the dyeability of the polymer. For example, a poly(epsilon-caprolactam) yarn of decreased dyeability can be combined with normal poly(epsilon-caprolactam) yarn in carpets and fabrics. When dyed, a two-tone effect results due to the variance in dyeability between the treated and untreated polyamide. This effect is sometimes accomplished by using certain dye-resists such as the soluble sulfur-phenol condensatcs which are applied directly to the finished fibers or yarn prior to weaving or tufting. However, the use of dye-resists with poly(epsilon-caprolactam) yarn is unsatisfactory because they often impair the light fastness of the finished product. Fabrics treated in this manner tend to fade quickly when exposed to ultraviolet light and are therefore undesirable in a number of end uses. Moreover, certain dye-resists produce a decrease in the light stability of the yarn itself thereby diminishing the strength of the yarn upon exposure to sunlight.

It is therefore an object of this invention to provide lighter-dyeing synthetic linear polyamide fibers and yarns not having the aforementioned disadvantages.

Another object of this invention is to provide a process for decreasing the dyeability and improving the light stability of poly(epsilon-caprolactam).

Still another object of this invention is to provide a modified fiber-forming poly(epsilon-caprolactam) that will resist the action of conventional acid dyestuffs to a limited degree and when dyed will not fade when exposed to sunlight.

A further object of this invention is to provide a modifiecl fiber-forming poly(epsilon-caprolactam) possessing decreased dyeability properties and an improved resistance to light degradation.

These and other objects will become apparent from the following detailed description.

In accordance with this invention, it has been discovered that a synthetic linear polyamide such as poly(epsiloncaprolactam) can be modified to possess decreased dyeability properties by incorporating into the polymer melt prior to fiber formation a small amount of butyrolactone.

3,328,341 Patented June 27, 1967 Not only does the product have reduced dyeability properties but it also possesses a greater resistance to degradation from ultraviolet light and when dyed is lightfast. The process is applicable generally to all synthetic linear polyamides having NH end groups. It is particularly desirable for use with those polyamides having a greater afiinity for dyes such as poly(epsilon-caprolactam). Without intending to be bound thereby, it is believed that the butyrolactone reacts with the amino end groups in the polymer and thus reduces a portion of the acid dye sites normally present therein. The modified polymer will then have hydroxy end groups in place of the amino end groups. Alternately, water may split out resulting in cyclic end groups. In either case, the amino group is effectively blocked from reaction with acid dyes. While the modified polyamide may be dyed with any of the conventional dyes used in dyeing nylon 6 and nylon 66, only the acid dyes and premetalized acid dyes produced the desired lighter dyeing results since the effective dyeing of each is reduced due to the reduction in amino groups or dye sites in the polymer chain.

The amount of butyrolactone added to the fiber-forming synthetic linear polyamide can be varied, depending on the results desired. Amounts less than 0.2% by weight butyrolactone based on the weight of the polyamide are in general too little to cause any appreciable blocking of dye sites and attendant lowering of dyeability in the polymer. While there is no upper limit to the amount of butyrolactone which can be added, it has been found that amounts above 3% cause considerable difliculties in spinning and processing of the polymer prior to fiber or filament formation. Preferably, amounts of butyrolactone ranging from 1% to 2% by weight based on the weight of the polyamide are employed in the process.

The figure shows graphically the relationship between the butyrolactone concentration in the polymer based on the amount added to the chips and the amino end groups and carboxyl end groups present in the polymer.

The butyrolactone may be incorporated into the preformed polymer in a number of ways. For example, it may be added directly to the polymer melt in any stage of the process prior to extrusion. In one method, it is added to granules or chips of the polymer prior to melt formation and thoroughly tumbled therewith to effect adequate mixing. In the preferred practice of the invention, the process comprises adding butyrolactone to the poly(epsilon-caprolactam) chips immediately after they have been tumble-dried to remove excess moisture and thus are still hot, i.e. a temperature of 95 C. Addition of the butyrolactone to the hot chips results in better absorption and more freely flowing chips which aids in chip transportation during subsequent operations. If the addition takes place before the chips are dried, substantial loss of butyrolactone is experienced due to evaporation in the dryers. Following addition, the chips and butyrolactone are thoroughly tumbled or otherwise mixed to produce a uniform mixture of chips and butyrolactone prior to melt formation. Thereafter, the chips are passed to a conventional melting device and extruded or spun at a temperature ranging from 265 C. to 280 C.

Conventional melting and spinning procedures and equipment customarily used in the production of polyamide fibers may be used with the butyrolactone modified polymer and the fiber product may be drawn and processed into yarn by any known means. The modified J poly(epsilon-caprolactam) yarn product can then be woven with normal poly(epsilon-caprolactam) yarn into fabrics or tufted into carpets, and when dyed with a single acid dye using standard procedures a striking two- 4 Example III An undyed carpet sample prepared in the manner described in Example I was immersed for 60 minutes in a boiling dyebath maintained at pH 8-9 and which conefieci is ploduced in the finished Product Further tained 0.4% of an acid premetalized yellow dye and dyemg Wlth dlsperse dyes can produce a two'color 1.39% of C. I. Disperse Blue 3, an anthraquiuone dye Product designated by Colour Index No. 61505. The resulting purposes oflnustfanon. the.fon0wu.1g examples are carpet was a contrasting blue/green showing that the However the Invention not Intended to be modified yarn picked up much less of the acid dyestuit hmlted thereby 10 producing an overall blue color from the disperse dye Example I whereas the untreated control accepted greater amounts Fiber-forming poly(epsilon-caprolactam) chips, preof the yellow acid dye such the end result was a green pared by conventionally polymerizing epsiloncapr01actam due to the combined, efiect of the acid yellow and disand extruding and chopping the polymer into chips, were perse blue dyes. dried at 90-95 C. in a tumble dryer to remove mois- Example IV immediately following drying and While the chlps A series of weatherometer tests were run to show the were In the qryer and Sun by welght butyrqlac' improved light stability of butyrolactone modified poly tone spnnkled q chlps and thoroughly mlxed (epsilon-caprolactam) over untreated poly(epsilon-caprothefewlth by Humming m the dryer The thus'treated lactam). A twin carbon arc Atlas Weather-Ometer that chips were conventlonally melt spun and processed to had been modified to give a more severe exposure was give a 1090 demer 83 filament A control yarn used for the tests. The samples were exposed at 190 F. sample was also prepared using identical polymerization, to the light f 22 minutes and then to vapor from a Spinning, and Processing Conditions except that the y shielded water spray for 60 minutes. The data is set forth lactone addition was eliminated. Both yarns were tufted 25 i h t bl bglow fo 200 d i 32 fil t yam into a carpet in alternating rows of modified yarn with pared in the same manner as that described in Example 1.

Sample Original Properties 80-Hour Wcatherometer 120Hour Weatherorneter (Test Data) (Test Data) Percent Tenacity Elongation Tenacity Elongation Tenacity Elongation Butyrolactone (g.p.d.) Percent (g.p.d.) Percent (g.p.d.) Percent 4. 32 38.5 2. 90 13. 4 1. 66 7. 5 0. 5 4. 32.1 4. 03 22. 3 2. 70 10.2 0. 75 4. 66 35. 4 3. 73 13. 3 2. 7s 10. 0 1. 0 4. 39 32. 0 3. 53 16.8 2.40 9.8 1.25 4.34 27.2 3.33 22.7 2.90 11.8 1. 5 4. 39 30. 9 3.67 19. 9 2. 51 10.0 1. 75 4. 30 26. 9 3.36 15. 3 1.98 7. 0 2. 0 4. 42 2s. 3 3. 5s 14. 7 2. 27 8.6

control yarn. Several samples of this carpet were then 45 The above data clearly shows that the modified polyconventionally dyed with different acid dyes. One of the mer has much improved light stability properties over the dyes used was C.I. Blue Acid 92, a monazo dye, the control polymer when treated under identical conditions. chemical constitution of which is designated by Colour While the invention has been described with particu- Index No. 13,390. In each case the modified poly(epsilonlarity in connection with poly(epsilon-caprolactam), it caprolactam) yarn dyed considerably lighter than the conis applicable generally to numerous other polyamides to tr01 Y Producing a Striking contrast in the 'P produce a decrease in dyeability and still retain light fast- Ah identical group of harpet Samples Were Similarly ness when dyed. The invention is therefore intended to dyed with acid Premetalized dyes The modlfied Y be limited only to the extent set forth in the following showed a lower degree of dyeability than the control yarn claims in each sample resulting in an excellent contrast in the What[ is claimedis: carpet. The carpet samples dyed with both the acid y 1, A process for decreasing the dyeability of fiberand premstahzed acld .dyes Y .excenent hght f forming polyamides comprising dispersing in a melt of a ness when exposed to direct sunlight 1n both the modified pmformed l id olymer at least 0.2% by weight yarn and normal yam Secuons' butyrolactone based on the weight of the polyamide.

Example 11 50 2. The process of claim 1 in which the polyamide is Polyamide chips prepared in the same manner as those P p p of Example I were treated with 1% by weight butyrolac- The Process of Claim 1 in which from i0 210% tone in a tumble dryer immediately following complebutyrolactone is dispersed in the polyamide melt. tion of the drying operation and while the chips were 4. A process for producing lighter dyeing poly(epsilonstill hot. Thorough mixing was effected by further tumcaprolactam) fibers and filaments having an improved bling and the polymer was conventionally melt spun and light stability comprising mixing butyrolactone with granprocessed into 1090 denier, 83 filament yarn. Untreated ule of a preformed poly(epsilon-caprolactam) polymer control yarn prepared identically except that the butyroin amounts of at least 0.2% by weight based on the weight lactone addition was eliminated was tufted into carpets of the polymer, and thereafter melting the mixture and exin alternating rows with the butyrolactone modified yarn. truding it into fibers and filaments. Aseries of samples of this carpet was conventionally dyed 5. The process of claim 4 in which from 1.0% to with the same acid dyes and premetalized dyes used in 2.0% butyrolactone are mixed with said polymer. Example I. Good contrast resulted in each sample between 6. A process for decreasing the dyeability and imthe modified yarn and control yarn. proving the light stability of poly(epsilon-caprolactam) 5 6 fibers and filaments comprising mixing butyrolactone References Cited with hot granules of a preformed poly(epsilon-capro- UNITED STATES PATENTS lactam) polymer in amounts of at least 0.2% by weight 2,705,227 3/1955 Stamatofi based on the Weight of the polymer, and thereafter melt- FOREIGN PATENTS ing the mixture and extruding it into fibers and filaments. 756 384 9/1956 G B 7. The process of claim 6 in which the butyrolactone is feat added to the hot granules after they have been dried to DONALD E. CZAJA, Primary Examiner.

remove excess moisture, said granules being at a tem- LEON BERCOVITZ, TWELSH, perature ranging from 90-95" C. 10 Assistant Examiners. 

1. A PROCESS FOR DECREASING THE DYEABILITY OF FIBERFORMING POLYAMIDES COMPRISING DISPERSING IN A MELT OF A PREFORMED POLYAMIDE POLYMER AT LEAST 0.2% BY WEIGHT BUTYROLACTONE BASED ON THE WEIGHT OF THE POLYAMIDE. 